Getting java.lang.AbstractMethodError when I test using REST Assured

Because of rest-assured 4.3.0 upgrade the Groovy from 2.5.7 to 3.0.2, see rest-assured/changelog.txt at master · rest-assured/rest-assured, you can specified the groovy version in pom file.

  <properties>
    <rest-assured.version>4.3.0</rest-assured.version>
    <groovy.version>3.0.2</groovy.version>
  </properties>

It looks like a bug in REST Assured 4.3.0, your code works with 4.2.0 version.

I didn't find opened issue. https://github.com/rest-assured/rest-assured/issues